Wegener's granulomatosis is a multisystem disease often with protean manifestations. Eye signs and symptoms can be prominent and may be the patient's initial complaint. For a definitive diagnosis of Wegener's granulomatosis, a tissue biopsy specimen must show vasculitis and necrotizing granuloma. The presence of anticytoplasmic autoantibodies in the serum of patients has been found to be highly specific for Wegener's granulomatosis and can considerably facilitate early diagnosis and be used to monitor disease activity. In two illustrative cases, the utility of this laboratory test in the differential diagnosis of scleritis and orbital pseudotumor is demonstrated.